The present invention relates to the treatment of natural lumina or tracts of the human or animal body through which a transit or flow of a fluid is effected, in particular a body fluid, either liquid or gaseous, on either side of a sphincter. The urinary, respiratory, digestive, and gynecological tracts constitute natural lumina within the meaning of the present invention.
"Treatment" is understood to mean both an intervention of a mechanical type, aiming to re-establish a flow which has previously been disturbed or prevented on account of an obstruction or a stenosis of the natural lumen, and also a treatment or intervention with a therapeutic objective, for example, to control the cicatrization of the wall of the natural lumen after surgical intervention, or to reduce hyperplasia of an organ or gland surrounding this same lumen.
The present invention will be introduced, defined and described, by way of a non-limiting example, with reference to the endo-urethral prostheses which are used in the urethra in connection with the striated muscular sphincter.
In accordance with the document FR-A-2 667 783, an endo-urethral prosthesis has been described which consists of a tubular element, of general cylindrical shape, whose wall comprises a relatively smooth and soft biocompatible material, for example a silicone rubber, at least in its outer part. This tubular element is sufficiently flexible to conform to the anatomical profile of the urethra and to its movements, but sufficiently rigid, particularly in the radial or diametral direction, to maintain an artificial passage in the urethra. This tubular element is intended to be placed in the urethra, without passing through the striated muscular sphincter, in the prostatic segment and/or in any one of the membranous, bulbar, perineal, and penile segments.
"Tubular element" is understood to mean any element whose outer surface is described by a generatrix corresponding to a straight or curved line, or other line, about an axis.
According to the document FR-A-2 667 783, the tubular element is supported in the urethra principally by the elastics bearing of the wall of said element, in radial extension, against the urethral wall, and secondarily by various notches formed in the wall of the same tubular element, freeing catches which fasten on the urethral wall, somewhat in the manner of scales.
In practice, such a prosthesis is not self-stabilizing, for various reasons:
the elastic bearing of the tubular element is insufficient to support it in position in the urethra, except by providing or obtaining a very substantial bearing which is likely to damage the urethral wall, leading to the patient experiencing pain, and in any case rendering the withdrawal of the implanted prosthesis difficult or impossible, PA1 the fastening catches, or scales, cooperate with the urethral wall, in its longitudinal direction, only in the sense of precluding or limiting the descent of the prosthesis; these fastening catches cannot therefore prevent the prosthesis from ascending, PA1 the externally smooth nature of the tubular element encourages its natural sliding against the urethral wall, in particular during the various movements of the urethra, PA1 and, finally, the various notches constitute as many punctiform bearing surfaces, or zones of turbulence, on which both the static pressure and the dynamic pressure of the urinary flow act during miction; this has the result of encouraging the descent of the urethral prosthesis. PA1 on the one hand, the self-stabilization which presupposes in one way or another, in the previous solutions, a certain anchoring of the prosthesis on the mucosa of the urethral wall, PA1 and, on the other hand, ease of introduction and especially of withdrawal of the prosthesis, that is to say its reversibility.
In accordance with the document WO91/16005, metal prostheses are furthermore known which consist of two elements, each consisting of metal coils, either contiguous or non-contiguous, which are intended to be arranged in the urethra on either side, respectively, of the striated muscular sphincter. For each element, these coils, which are compressible in a centripetal manner and are expansible in a centrifugal manner, define, in their expanded position, an enveloping surface with a cross section varying from one end to the other.
Prostheses are also known which consist of a metallic or non-metallic tube which is perforated and is expansible at the moment of its implantation in the urethra.
At present, the various urethral prostheses proposed and described have been unable to reconcile: